The invention relates generally to semiconductor device fabrication and, in particular, to device structures for a varactor, methods of forming device structures for a varactor, and design structures for a varactor.
Semiconductor devices known as varactors have a capacitance that can be varied by varying a bias voltage applied from a back electrode. Varactors are found in many complementary metal-oxide-semiconductor (CMOS) integrated circuits in circuit designs for certain applications, such as radiofrequency (RF) communications and RF wireless applications. Varactors are particularly useful as active elements in parametric circuits, such as oscillation circuits like voltage-controlled oscillators, in which the capacitance tunability of the varactor is advantageously used to tune the circuit's oscillation frequency.
Device structures, fabrication methods, and design structures are needed that improve upon conventional varactors.